Copy and paste it in your userconfig.cfg

Credits.

I have made it by myself.

Код:
bind "mouse5" "unbind MWHEELUP invprev;bind MWHEELUP +jump; unbind MWHEELDOWN invprev; bind MWHEELDOWN +duck; "

bind "mouse4" "unbind MWHEELUP +jump; bind MWHEELUP invprev; unbind MWHEELDOWN +duck; bind MWHEELDOWN invnext; "